Additive manufacturing with dispensing of multiple powders

ABSTRACT

An additive manufacturing apparatus includes a platform, one or more supports positioned above the platform, an actuator, a first dispenser system configured dispense a plurality of successive layers of powder onto a build area supported by the platform, a first binder material dispenser configured to selectively dispense a first binder material on a voxel-by-voxel basis to an uppermost layer of powder in the build area, and an energy source configured to emit radiation toward the platform so as to solidify the binder material. The first dispenser system includes a first powder dispenser that is attached to and moves with a first support from the one or more supports and is configured to selectively dispense a first powder onto the build area, and a second powder dispenser that is configured to selectively dispense the second powder onto the build area.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Application Ser. No.62/611,289, filed on Dec. 28, 2017, the disclosure of which isincorporated by reference.

TECHNICAL FIELD

This specification relates to powder dispenser systems, binderdispensing systems, and energy delivery systems for additivemanufacturing apparatuses, e.g., for manufacturing of a green part.

BACKGROUND

Additive manufacturing (AM), also known as solid freeform fabrication or3D printing, refers to a manufacturing process in whichthree-dimensional objects are built up from successive dispensing of rawmaterial (e.g., powders, liquids, suspensions, or molten solids) intotwo-dimensional layers. In contrast, traditional machining techniquesinvolve subtractive processes in which articles are cut out from a stockmaterial (e.g., a block of wood, plastic or metal).

A variety of additive processes can be used in additive manufacturing.Some methods melt or soften material to produce layers, e.g., selectivelaser melting (SLM) or direct metal laser sintering (DMLS), selectivelaser sintering (SLS), fused deposition modeling (FDM). Some methodscure liquid materials using different technologies, e.g.,stereolithography (SLA). Some systems place binder materials onto layersof feed materials, e.g., powder, and use energy sources to cure thebinder materials to bond loose powder particles together.

Some dry powder additive manufacturing apparatuses, such asbinder-jetting 3D printers, can produce parts in a variety of materials.A typical binder jetting additive manufacturing process includesspreading a first uniform layer of powder across the platform. Thepowder particles can be of metal, ceramics, sand, plastic, a mixture ofdifferent materials, etc. The additive manufacturing apparatus thendeposits binder materials onto the layer of powder at locationscorresponding to a layer of the object to be fabricated. An energysource is used to cure the binder materials in order to bond powderparticles together. After the binder material has been cured in thelayer, the apparatus then spreads a second uniform layer of powder ontop of the first layer, and repeats the binder depositing and curingsteps. Once the apparatus finishes spreading all layers, athree-dimensional “green” part is formed within the pool of loosepowder. The part is “green” in that the main constituent, i.e., thematerial provided by the powder, is held together by the bindermaterial, and has not yet been sintered or fired to solidify the powderinto a solid mass of material. The green part is formed of powder gluedtogether by cured binder agents, and has a vertical spatial resolutionequal to the thickness of each layer of powder. The loose powderparticles can be recycled and stored for the next print. Depending onthe type of powder particles, the green part may serve as the finalproduct, or it may need to go through additional post-processing steps,such as annealing or sintering, hot isostatic pressing, etc., to formthe final product.

SUMMARY

In one aspect, an additive manufacturing apparatus includes a platform,one or more supports positioned above the platform, an actuator coupledto at least one of the platform and the one or more supports andconfigured to create relative motion therebetween such that the one ormore supports scan across the platform, a first dispenser systemconfigured dispense a plurality of successive layers of powder onto abuild area supported by the platform, a second dispenser systemconfigured to dispense a binder material onto the build area, and anenergy source configured to emit radiation toward the platform so as tosolidify the binder material. The first dispenser system includes afirst powder dispenser that is attached to and moves with a firstsupport from the one or more supports and is configured to selectivelydispense a first powder onto the build area. The second dispenser systemincludes a first binder material dispenser configured to selectivelydispense a first binder material on a voxel-by-voxel basis to anuppermost layer of powder in the build area to form a volume of thelayer having powder and binder material and corresponding to across-sectional portion of a part being built.

Implementations may include one or more of the following features.

The first support may be movable along a first axis, and the firstpowder dispenser may be configured to selectively dispense the powder ina strip along a second axis that is at a non-zero angle, e.g.,perpendicular, relative to the first axis. The first powder dispensermay be configured to selectively dispense the powder on a voxel-by-voxelbasis along the second axis, or on a region-by-region basis along thesecond axis where regions are larger than voxels.

The first binder material dispenser and energy source may be attached toand move with the first support. The first binder material dispenser maybe configured to selectively dispense the binder material in a stripalong the second axis. The first binder material may include adensification material.

The first binder material dispenser and energy source may be attached toand move with a second support from the one or more supports, the secondsupport may be movable along a third axis, and the first binder materialdispenser may be configured to selectively dispense the binder materialin a strip along a fourth axis that is at a non-zero angle, e.g.,perpendicular, relative to the third axis. The third axis may beparallel to the first axis. The fourth axis may be parallel to the thirdaxis. The first support and the second support may be connected to andindependently movable on a guide rail. The first support may be movableon a first guide rail and the second support may be movable on a secondguide rail parallel to the first guide rail. The third axis may beperpendicular to the first axis. The fourth axis may be perpendicular tothe third axis.

The first powder dispenser may be configured to selectively dispense thepowder on a voxel-by-voxel basis. The first powder dispenser may beconfigured to selectively dispense the powder on a region-by-regionbasis, where regions are larger than voxels. The first powder dispensermay have a first plurality of individually controllable orifices, eachorifice of the first plurality of orifices configured to controllablydeliver the first powder. The first powder dispenser may span a width ofthe build area. The first dispenser system may include a plurality offirst powder dispensers, each first powder dispenser attached to thefirst support. The plurality of first powder dispensers may be arrangedin a staggered pattern so as to cover a width of the build area.

A controller may have a memory configured to store a data object thatidentifies a pattern in which the binder material is to be solidified ina layer of an object to be fabricated. The controller may be configuredto configured to, for the layer, cause the actuator to create relativemotion between the support and the platform, cause the first dispensersystem to dispense a layer of powder in regions that encompasses thecross-sectional portion of the part being built as the support scansacross the platform, cause the second dispenser system to dispense alayer of binder material on the layer of powder in the pattern based onthe data object to provide the combined layer of powder and bindermaterial corresponding to the cross-section of the part being built, andcontrol the energy source to solidify the binder material in thecombined layer in accord with the pattern.

A third dispensing system may be configured to deliver a densificationmaterial to the layer of powder or the combined layer of powder andbinder material. The densification material may have a same compositionas the powder but have a smaller mean diameter. The third dispensersystem may include a first densifier dispenser configured to selectivelydispense the densification material onto the build area. The firstdensifier dispenser may include a plurality of individually controllableorifices, each orifice of the plurality of orifices of the firstdensifier dispenser configured to controllably deliver the densifyingmaterial.

The first densifier dispenser may be attached to and moves with thefirst support. The first binder material dispenser and energy source maybe attached to and move with the first support, or attached to and movewith a second support from the one or more supports. The first supportmay be movable along a first axis, and wherein the second support ismovable parallel to the first axis independently of the first support.The first support may be movable along a first axis, and the secondsupport may be movable perpendicular to the first axis independently ofthe first support. The first support may be movable along a first axis,the second support may be movable along a second first axisindependently of the first support, and the first binder materialdispenser may be is configured to selectively dispense the bindermaterial in a strip along an axis that is at a non-zero angle relativeto the second axis.

The first densifier dispenser may be attached to and moves with a secondsupport from the one or more supports, and the second support may bemovable along a third axis. The first densifier dispenser may beconfigured to selectively dispense the densifier material in a stripalong a fourth axis that is at a non-zero angle relative to the thirdaxis. The third axis may be substantially parallel to the first axis.The first binder material dispenser and energy source may be attached toand move with the second support.

The first binder dispenser and first densifier dispenser may beconfigured such that the first binder dispenser is positioned before thefirst densifier dispenser along the direction of motion. The firstbinder dispenser and first densifier dispenser may be configured suchthat the first binder dispenser is positioned after the first densifierdispenser along the direction of motion.

The third dispenser system may include a second densifier dispenserconfigured to selectively dispense the densification material onto thebuild area. The first densifier dispenser and second densifier dispensermay be attached to and move with the first support. The first densifierdispenser may be attached to and move with a second support from the oneor more supports and the second densifier dispenser may be attached toand move with a third support. The first binder dispenser and energysource may be attached to and move with a fourth support from the one ormore supports. The densification material may have a same materialcomposition as the powder but a smaller mean diameter particle size.

A fourth dispenser system may be configured to dispense a plurality ofsuccessive layers of a second powder onto the build area, wherein thefourth dispenser system comprises a second powder dispenser that isconfigured to selectively dispense the second powder onto the buildarea. The second powder may differ in composition from the first powder.The first powder may include metallic particles and the second powdermay include ceramic or plastic particles. The first powder may includeceramic particles and the second powder include plastic particles. Thesecond powder may have a same material composition as but a differentsize distribution than the first powder.

The second powder dispenser may include a plurality of individuallycontrollable orifices, each orifice of the plurality of orifices of thesecond powder dispenser configured to controllably deliver the secondpowder. The second powder dispenser may be attached to and move with thefirst support. The first binder dispenser and the energy source may besupported by the first support, or may be supported by and movable witha second support from the one or more supports. The second powderdispenser may be supported by and movable with a second support from theone or more supports.

The second support may be movable along a third axis, and the secondpowder dispenser may be configured to selectively dispense the secondpowder in a strip along a fourth axis that is at a non-zero anglerelative to the third axis. The first binder material dispenser andenergy source may be attached to and move with the second support, orattached to and move with a third support from the one or more supports.The third axis may be substantially parallel to the first axis. Thefourth axis may be substantially parallel to the second axis. The fourthaxis may be perpendicular to the third axis. The first powder dispenserand second powder dispenser may be configured such that the first powderdispenser is positioned before the second densifier dispenser along thedirection of motion. The third axis may be substantially perpendicularto the first axis. The first support and second support may be movableon a same guide rail, or movable on separate parallel guide rails.

A controller may have a memory configured to store a data object thatcorresponds to at least a layer of an object to be fabricated, and thecontroller may be configured to configured to cause the first dispensersystem to dispense the first powder in a region corresponding to theobject to be fabricated, and cause the fourth dispenser system todispense the second powder in a region that does not correspond toobjects to be fabricated.

The first powder may include metal particles and the second powder mayinclude ceramic particles. The first powder may include metal or ceramicparticles and the second powder may include plastic particles. Thecontroller may be configured cause the first dispenser system todispense binder material on only the first powder. The controller may beconfigured cause the first dispenser system to dispense binder materialon both the first powder and the second powder.

A controller having a memory configured to store a data object thatcorresponds to at least a layer of an object to be fabricated, and thecontroller configured to configured to cause the first dispenser systemto dispense the first powder in a first region corresponding to theobject to be fabricated, cause the fourth dispenser system to dispensethe second powder in a portion of the first region. The second powdermay include a densification material for the first powder. The firstdispenser system may include a second powder dispenser to dispense thefirst powder and the second dispenser system may include a second bindermaterial dispenser to dispense the binder material. The first powdermaterial dispenser, second powder material dispenser, first bindermaterial dispenser and second binder material dispenser may be attachedto and move with the first support. The first binder material dispenser,second binder material dispenser, and energy source may be are attachedto and move with a second support, and the second binder materialdispenser is attached to and moves with a third support. The firstsupport, second support and third support may be independently movablealong the first axis. Along the third axis the first powder dispenser,first binder material dispenser, energy source, second binder materialdispenser and second powder dispenser may be arranged in theaforementioned order.

A controller may have a memory configured to store a data object thatidentifies a pattern in which the binder material is to be solidified ina successive layers of an object to be fabricated, and the controllermay be configured to configured to cause the first powder dispenser todispense a first layer of powder as the first powder dispenser moves ina first direction along the first axis, cause the first binder dispenserto dispense a first layer of binder material on the first layer ofpowder to provide a first combined layer of powder and binder materialas the first binder material dispenser moves in the first directionalong the first axis, control the energy source to solidify the bindermaterial in the first combined layer in accord with the pattern, causethe second dispenser system to dispense a second layer of powder as thesecond powder dispenser moves in a second direction opposite to thefirst direction along the first axis, cause the second binder dispenserto dispense a second layer of binder material on the second layer ofpowder to provide a second combined layer of powder and binder materialas the second binder dispenser moves in the second direction, andcontrol the energy source to solidify the binder material in the secondcombined layer in accord with the pattern.

The light source may be configured to illuminate a stripe along of theuppermost layer. The energy source may be coupled to a support from theplurality of supports, and the support may be movable along an axis at anon-zero angle, e.g., a right angle, relative to the stripe to sweep thestripe across the build area. The energy source may include a pluralityof independently controllable light sources. The light sources may belight emitting diodes (LEDs). The light sources may be UV or IR lightsources.

An oven may sinter a green part fabricated on the platform. A robot maytransfer the green part from the platform to the oven. An etching systemmay etch away the binder material. A sealed housing may form a chamberenclosing the platform, one or more supports, first dispenser system,second dispenser system and energy source. A pump may evacuate thechamber. A gas supply may provide a gas that is inert to the firstpowder and the first binder material.

In another aspect, a method of fabricating a green part includessuccessively forming a plurality of layers of the green part by, foreach layer, selectively dispensing a layer of powder onto a build areaon a platform, wherein the selective dispensing covers less than all ofthe build area, selectively dispensing a binder material onto the layerof powder to form a combined layer of powder and binder material, anddirecting radiation toward the platform so as to solidify the bindermaterial to form a layer of the plurality of layers of the green part inwhich the powder is held by the solidified binder material.

Implementations may include one or more of the following features. Thegreen part may be removed from the platform and processed to form thepowder into solid mass. Processing comprises one or more of annealing,sintering, and/or hot isostatic pressing.

Selectively dispensing the layer of powder may include dispensing powderfrom a plurality of independently controllable nozzles of a powderdispenser while the powder dispenser moves along a first axis. Thenozzles are arranged along a second axis at a non-zero angle, e.g., aright angle, relative to the first axis.

Selectively dispensing the binder material may include dispensing bindermaterial from a plurality of independently controllable nozzles of abinder material dispenser while the binder material dispenser movesalong a third axis. The nozzles may be arranged along a fourth axis at anon-zero angle relative to the third axis. The third axis may beparallel or perpendicular to the first axis. The fourth axis may beperpendicular to the third axis.

Radiation may be directed toward the platform by delivering energy alonga stripe that is parallel to the fourth axis. A constant distance may bemaintained between the third axis and the stripe of radiation duringprocessing of a layer. Maintaining the constant distance may includesecuring the binder material dispenser and a light source to a samesupport. Directing radiation toward the platform may include selectivelydelivering energy along the stripe.

Selectively dispensing the layer of powder may include determining aperimeter of a cross-sectional area covered by the part, determining abuffer zone surrounding the perimeter of the cross-sectional area, anddispensing powder into regions that overlap the cross-sectional area andbuffer zone. Selectively dispensing the layer of powder may includedetermining a retaining wall region surrounding the buffer zone, anddispensing powder into regions that overlap the cross-sectional area,buffer zone and retaining ring area. Binder material can be refrainedfrom being dispensed to the buffer zone. Powder can be refrained frombeing dispensed outside the regions that overlap the retaining ringarea. The layer of powder may be dispensed from a first dispenser, thebinder material may be dispensed from a second dispenser, and theradiation may be generated from an energy source, and the firstdispenser, second dispenser and energy source may be lifted by a heightapproximately equal to a thickness of the layer after each layer isprocessed.

Particular embodiments of the subject matter described in thisspecification can be implemented so as to realize one or more of thefollowing advantages. Selective material dispensing in additivemanufacturing can reduce feedstock wastage and contamination, and canimprove manufacturing efficiency. The presence of densification materialcan increase product rigidity and reduce product shrinkage duringpost-processing.

The details of one or more implementations of the subject matterdescribed in this specification are set forth in the accompanyingdrawings and the description below. Other potential features, aspects,and advantages will become apparent from the description, the drawings,and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-B each shows a schematic top view of an implementation of anaddictive manufacturing apparatus.

FIG. 1C shows a schematic side view of an addictive manufacturingapparatus, e.g., the additive manufacturing apparatus of FIG. 1A.

FIG. 1D shows a schematic side view of an implementation of a printheadassembly.

FIGS. 2A-2C each shows a schematic top view of an implementation of anadditive manufacturing apparatus.

FIGS. 3A-3E each shows a schematic top view of an implementation of anadditive manufacturing apparatus.

FIG. 4A-B show examples of an additive manufacturing apparatus at work.

FIG. 5A-B show an example of a powder dispenser selectively dispensingpowder.

FIG. 6 is a flow chart of a process used to form one or more greenparts.

DETAILED DESCRIPTION

In current dry powder additive manufacturing apparatus for forming greenparts, the powder dispenser system spreads powder across the entirebuild area during operation. For example, such an apparatus can employrollers or blade recoaters to push a pool of feed materials across thebuild area. As a result, powder is distributed to regions of the buildarea that do not correspond to the part being fabricated.

The excessive usage of powder, however, causes several drawbacks on bothproduct quality and manufacturing efficiency. In particular, asignificant portion of powder is wasted, increasing part cost. Recyclingof powder may be impractical, expensive, or lead to poor part quality.For example, recoating using reclaimed powder significantly increasesthe chances of powder contamination. Examples of powder contaminationinclude but are not limited to binder material contamination, sinteringcontamination, oxygen contamination, etc. Contaminated powder particleshave direct impact on the final part's quality. Furthermore, powder hasto be applied to areas where actual printing does not occur, thusslowing down the system's overall print speed and/or throughput.

A technique to address some of these issues is to use a binder-jettingadditive manufacturing apparatus in which powder can be selectivelydelivered over the build area. Such an apparatus can reduce powderusage, increase the efficiency of printing, and reduce the possibilityof powder contamination.

The powder dispenser system can employ an array of individuallycontrollable nozzles. As the powder dispenser moves across the platform,the powder dispenser nozzles can be independently activated to dispensepowder only at selected locations on the platform.

Furthermore, binder-jetting processes often result in low compaction ofthe green part and hence excessive shrinkage during post-processing. Thepresence of binder material particles between the powder particlesfurther creates space for potential source of defects duringpost-processing. However, an additive manufacturing apparatus caninclude densification materials in binder formula to reduce the voidsbetween dispensed particles in a layer. The densification materials canalso serve as nucleation site during post-processing to improve thestrength of the final product.

An additive manufacturing apparatus can be made in differentconfiguration to improve printing efficiency.

The additive manufacturing apparatus includes at least a platform thatprovides a build area on which the part is to be fabricated, a powdermaterial dispenser, a binder material dispenser, and an energy source todeliver energy to cure the binder material. The powder materialdispenser, binder material dispenser, and energy source can be held byone or more supports above the platform.

FIG. 1A shows an example of the top view of an additive manufacturingapparatus 100. The additive manufacturing apparatus 100 includes aplatform 102 that provides a build area on which the part is to befabricated, a support 104 positioned above the platform 102, and aprinthead assembly 103 mounted on the support 104.

The various components, e.g., platform 102, support 104 and printheadassembly 103, can be enclosed in a sealed housing 180 that provides acontrolled operating environment. The housing 180 can include an inlet182 coupled to a gas source, e.g. Ar, or N₂, and an outlet 184 coupledto an exhaust system, e.g., a pump. This permits the pressure and oxygencontent of the interior of the housing 180 to be controlled. Forexample, oxygen gas can be maintained below 50 ppm when dealing with Tipowder particles.

The additive manufacturing apparatus can include other features, e.g., aservice station 190 to purge and/or clean various components ofprinthead assembly 103, or a powder charging station 192 to reload thedispensers in the printhead assembly 103. These stations can also bepositioned inside the housing 180.

The printhead assembly 103 includes one or more printheads, eachconfigured to be independently removably secured to the support 104.Each printhead can include one or mechanisms to dispense a powdermaterial, a binder material, and/or a densification material. One of theprintheads, e.g., the printhead that includes a dispenser for the bindermaterial, can also include a mechanism to deliver energy to cure thebinder material. Alternatively or in addition, a mechanism to deliverenergy can be mounted directly to the support 104.

For example, FIG. 1D shows a schematic example of a printhead 103 a. Theprinthead 103 a includes a sensor 109 for a metrology system, one ormore powder dispensers 106 (e.g., two powder dispensers 106 a and 106b), one or more binder material dispensers 110 (e.g., two bindermaterial dispenser 110 a and 110 b), and one or more energy deliverysystems 112 (e.g., two energy delivery systems 112 a and 112 b). Thecomponents are mounted to a common frame 103 b, and the frame 103 b canbe removably mounted on the support 104. This permits the printhead 103a with the various components to be attached and detached as a unit fromthe support 104. Although FIG. 1D illustrates the components as beingsuspended below the frame 103 b, this is not necessary; the frame 103 bcould simply be a plate with apertures into which the components fit.

Returning to FIG. 1A, the support 104 is movable relative to theplatform 102 so that the printhead assembly 103 is movable over thebuild area. The additive manufacturing apparatus 100 includes one ormore actuators 127 a. The actuators 127 a are operable to createrelative motion between the support 104 and the platform 102, e.g.,along the X-axis, such that the support 104 and the printhead assembly103 can scan across the platform 102. For example, one or more rails 125a can be arranged adjacent the platform 102 and extending along anX-axis, and the support 104 can be supported on and movable along therails 125 a by the actuators 127 a. Where two rails are used, the rails125 a can be on opposite sides of the platform 102. For example, thesupport 104 can be a gantry supported on two opposite sides, e.g., bytwo rails 125 a, 125 b, as shown in FIG. 1A. Alternatively, the support104 can be held in a cantilever arrangement on a single rail.

In some implementations, the support 104 and the platform 102 can beconfigured to be immobile relative to each other along the Y-axis.Alternatively, one or more actuators 127 b can be used to createrelative motion between the support 104 and the platform 102 along theY-axis, e.g., as shown in FIG. 1B.

As shown in FIG. 1A, the printhead assembly 103 supports a powderdispenser 106, a densification material dispenser 108, a binder materialdispenser 110, and an energy delivery system 112. Each of theseprintheads is placed in a fixed position on the support 104 and relativeto each other. The printheads can be positioned in the printheadassembly 103 such that the printhead assembly 103 can finish printingone layer of material in a single motion. For example, along thedirection of motion, e.g., the x-axis, the powder dispenser 106 can beplaced before the densification dispenser 108 and the binder materialdispenser 110, and the energy delivery system 112 can be placed afterthe densification material dispenser 108 and the binder materialdispenser 110. As a result, the printhead assembly 103 can completeprinting of one layer in a single sweep in one direction across thebuild area.

The densification material dispenser 108 is optional, so in someimplementations and the printhead assembly includes only the powderdispenser 106, the binder material dispenser 110, and the energydelivery system 112.

In some implementations, the dispensers 106, 110 and energy deliverysystem 112 can be directly mounted to the support 104.

In some implementations, each of the respective printheads can bepositioned, relative to the platform 102 to deliver materials along arespective line at a respective non-zero angle, e.g., at a right angle,relative to the direction of motion of the support 104. The material canbe delivered by two or more of the printheads along parallel lines. Forexample, where the support 104 and printhead assembly 103 are movingalong the X axis, each printhead can deliver material along a line alongthe Y-axis.

The printheads can be configured to deliver materials along a line thatspans the entire build area of the platform 102. For example, in someimplementations (e.g., shown in FIG. 1A), each printhead spans theentire build area. Alternatively, the printhead assembly can includemultiple printheads arranged in two or more columns to form a staggeredarray such that each of the printheads spans across the entire platform102 along the Y-axis.

The energy delivery system 112 includes an energy source, e.g., lightsource, that generates and directs radiation toward the combined layerof powder and binder material. If the binder material is liquid, theenergy source can cure the binder material to solidify the bindermaterial. This can form a body having the powder suspended in a curedmatrix of binder material. The radiation from the energy delivery systemcan include UV light, IR light and/or visible light.

In some implementations, the energy source is configured to illuminate astrip that extends across a width of the build area, and to move theilluminated strip across the length of the build area to sweep theradiation beam across the entire build area. The strip can extend at anon-zero angle, e.g., perpendicular, to the direction of motion of thestrip. In some implementation, the energy source is secured to and moveswith a support, and the relative motion between the support and theplatform causes the strip of light to sweep across the build area.Alternatively, a light beam can be deflected from a rotatable mirror,and rotation of the mirror can move the strip of light.

In some implementations, the energy delivery system includes a pluralityof light sources that can be independently activated. Each light sourcescan be arranged in an array, e.g., a linear array, so as to provideselectable illumination along the primary axis of the strip. The energysources can include, for example, light emitting diodes (LEDs),configured to emit radiation having an intensity dependent on a currentdelivered to the LEDs. The energy sources can also include, for example,an array of lasers, e.g., laser diodes, an array of lamps, e.g., mercurylamps, that provide wide spectrum irradiation, or a solid-state infraredemitter array.

In some implementations, the energy sources are arranged such that eachradiation beam is directed toward a different voxel of the layer. Insome implementations, the energy sources are arranged such that eachradiation beam is directed toward a different region of the layer, withthe regions being larger than the voxels provided by the binder materialdispenser.

In some implementations, the actuator 127 a causes relative motionbetween the platform 102 and the support 104 such that the support 104advances in a forward direction relative to the platform 102. The powderdispenser 106, densification material dispenser 108, and the bindermaterial dispenser 110 can be positioned on the support 104 ahead of theenergy delivery system 112 so that the recently dispensed powder 116 canbe subsequently cured by the energy delivery system 110 as the support104 is advanced relative to the platform 102.

In some implementations, the platform 102 is positioned on a conveyoroperable to move the platforms along the X-axis. The actuator 127 a cangenerate linear motion of the conveyor along the X-axis, thereby causingrelative motion of the platforms 102 and the support 104.

In some implementations, the apparatus 100 includes multiple platforms102 arranged in a linear array or two-dimensional array.

In some implementations, the apparatus 100 can includes multiple powderdispensers with each dispenser configured to dispense a different typeof powder, e.g., different powders of different material composition.For example, in FIG. 1D, a first powder dispenser 106 a can dispensepowder comprising metal particles, and a second powder dispenser 106 bcan dispense powder comprising plastic particles.

In some implementations, apparatus includes multiple powder dispensersconfigured to dispense powder of the same composition but of differentsize. For example, in FIG. 1D, the powder dispenser 106 a can dispensepowder comprising metal particles larger than a first mean diameter, andthe powder dispenser 106 b can dispense powder comprising metalparticles smaller than the first diameter.

In some implementations, the assembly includes multiple binder materialdispensers that are configured to dispense different types of bindermaterials. For example, in FIG. 1D, the binder material dispensers 110 acan be configured to dispense a first binder material operable on powderfrom the powder dispenser 106 a, while the binder material dispenser 110b can be configured to dispense a second binder material operable onpowder from the powder dispenser 106 b.

The binder materials can differ in viscosity, curing wavelength, curingkinetics, and/or wetting behavior. The binder materials can be dispensedfrom respective binder material dispensers. In some implementations, afirst binder material has a sufficiently low viscosity than that thefirst binder material can interfiltrate swiftly through the layer ofpowder. In contrast, the second binder material can have a higherviscosity than the first binder material, e.g., a sufficiently highviscosity that the second binder material will bridge gaps betweenparticles to improve leveling of the layer. This can facilitate goodinterlayer adhesion.

In some implementations, the first binder material preferentially wetsthe powder, and the second binder material preferentially wets the firstbinder materials.

In some implementations, the first binder material cures more quicklythan the second binder material under normal radiation conditions. Thispermits the first binder material to quickly fix the powder in place,and the second binder material to hold the powder more securely. In someimplementations, the second binder material can be cured duringapplication of energy to a subsequently deposited layer.

FIG. 1B shows another example of an additive manufacturing apparatus100. The implementation shown in FIG. 1B is similar to theimplementation shown in FIG. 1A, but in FIG. 1B, the printheads 106-110and energy delivery system 112 mounted on the support 104 do not extendalong the entire width of the platform 102. For example, in FIG. 1B, thewidth of the powder dispenser 106 is shorter than the width of theplatform 102. As a result, the printhead assembly 103 is configured tobe movable relative to the platform 102 along an axis, e.g., Y-axis,that is at a non-zero angle, e.g., at a right angle, to the primarydirection of motion of the support 104. This permits the dispensers tocover the entire build area of the platform 102. The printhead assembly103 can be movably mounted to the support 104 so that each component canbe repositioned to dispense material or deliver energy across the entirewidth of the platform 102. In some implementations, one or moreactuators 127 b positioned on the support 104 and operable to move thecomponents of the printhead assembly 103 on the rails 125 b along theY-Axis relative to the support 104 and to the platform 102.

In some implementations, the powder dispenser 106 can extend, e.g.,along the Y-axis, using the actuator 127 b and along the rails 125 y,such that powder particles 116 are dispensed along a line, e.g., alongthe Y-axis, that is perpendicular to the direction of motion of thesupport 104, e.g., perpendicular to the X-axis. Thus, as the support 104advances along the direction of motion, powder particles 116 can bedelivered across the entire platform 102.

FIG. 1C shows an example of the side view of the additive manufacturingapparatus 100. The additive manufacturing apparatus 100 can include asensing system 109, e.g., to detect a height of the platform 102 or theheight of the top surface of the layers of powder 116. For example, thesensing system 109 can include one or more optical sensors, e.g. tomeasure a height of the topmost layer of powder 116 relative to bottomsurface of the printhead assembly 103.

The apparatus 100 can also include a controller 111 configured toselectively operate the actuator 127 c to create relative verticalmotion (i.e. along the Z-axis) between the printhead assembly 103 andthe platform 102. For example, the relative vertical motion can beachieved by moving the platform 102 or the support 104 along the rail125 c along the Z-axis. In particular, for heavy metal parts, thesupport 104 can be moved while the platform 102 remains stationary.

The controller 111 can be linked to the sensing system 109 such that thecontroller 111 uses data from the sensing system 109 to determine theappropriate height adjustment. For example, after each layer of powder116 is dispensed, the sensing system 109 determines the new distancebetween the top surface of the layer of powder 116 and the bottomsurface of the printhead assembly 103. The controller 111 receives thisdata and uses the actuator 127 c to raise the support 104 by theappropriate height equal to the height of the layer of the powder 116.Consequently, the apparatus 100 can maintain a constant height offsetbetween the top surface of the layer of powder 116 and the printheadassembly 103 from layer-to-layer.

In some implementations, the relative motion between the printheadassembly 103 and the platform 102 can be incremental or continuous. Forexample, the printhead assembly 103 can be moved relative to theplatform 102 between sequential dispensing operations, betweensequential curing operations, or both. Alternatively, the printheadassembly 103 can be moved continuously while the powder 116 is dispensedand is cured.

In some implementations, the additive manufacturing apparatus 100 caninclude multiple supports, and each support can mount one or moreprintheads or the energy delivery system. In some implementations, wheremultiple supports are used, each of the supports can be independentlymoveable in parallel.

FIG. 2A gives an example of a top view of another implementation of anadditive manufacturing apparatus 100. In FIG. 2A, the apparatus 100includes four supports 104 a-104 d. The powder dispenser 106 is mountedon the support 104 a. The densification material dispenser 108 ismounted on the support 104 b. The binder material dispenser 110 ismounted on the support 104 c. The energy delivery system 112 is mountedon the support 104 d.

In some implementations, each of the supports is independently moveablein parallel, e.g., along the Y-axis. For example, the support can becoupled to and moveable along the same rail, e.g., the rail 127 a, byrespective actuators. Alternatively, each of the supports can be coupledto different rails and can move independently and parallel to eachother.

In some implementations, some but not all components can be mounted onthe same support. For example, in FIG. 2B, the powder dispenser 106 andthe densification material dispenser 108 are mounted on the same support104 a in fixed position relative to each other and to the support 104 a.The energy delivery system 112 and the binder material dispenser 110 aremounted on a separate support 104 b in fixed position relative to eachother and to the support 104 b.

As another option, the densification material dispenser 108, binderdispenser 110 and energy source 112 could be mounted on the samesupport, and the powder dispenser 106 could be mounted on a separatesupport.

In some implementations, supports 104 a-104 d can be coupled to the samerail 125 a. Alternatively, the supports can be coupled to differentrails and can move independently and parallel to each other.

In some implementations, one or more printheads can be mounted ondifferent supports that move perpendicular to each other. For example,in FIG. 2C, support 104 b moves in the X-axis along rails 125 a, whilesupport 104 a moves in the Y-axis along rails 125 b. In this case, eachprinthead on support 104 b can deliver material along a line that is atright angle to the line along which material is delivered by eachprinthead on support 104 a.

In some implementations, the additive manufacturing apparatus caninclude multiple printheads of the same type (e.g., powder delivery,densification material delivery or binder material delivery). This canpermit the apparatus to operate in a bi-directional mode.

FIG. 3A shows an example of a top view of the additive manufacturingapparatus 100 with six printheads mounted on the single support 104 infixed positions relative to each other. The energy delivery system 112is positioned between the two binder material dispensers 110 a and 110b, the two binder material dispensers are positioned between the twodensification material dispensers 108 a and 108 b, and the twodensification dispenser are positioned between two powder dispensers 106a and 106 b. Alternatively, the positions of the densificationdispensers 108 a, 108 b and the binder material dispensers 110 a, 110 bcan be swapped. The actuator 127 a can create relative motion betweenthe support 104 and the platform 102 along the X-axis. For example, thesupport 104 can be movably coupled to the rails 125 x.

As shown in FIG. 3A, as the support 104 moves across the platform 102 inthe positive X-direction in a first scanning motion, the powderdispenser 106 a, the densification material 108 a, and the bindermaterial dispenser 110 a can sequentially deposit respective materialson the platform 102 to form a first layer of material matrix. Since thepowder dispenser 106 a, the densification material dispenser 108 a, andthe binder material dispenser 110 a are all positioned in advance to theenergy delivery system 112, the energy delivery system 112 cansubsequently cure this first layer of material to form a first layer ofthe green part. After this scanning motion, the support 104 will stop ata new position relative to the platform 102 as shown in FIG. 3B.

As shown in FIG. 3B, the support 104 then moves in the oppositedirection, i.e., the negative X-direction, to return to the initiallocation as shown in FIG. 3A. The powder dispenser 106 b, thedensification material dispenser 108 b, and the binder materialdispenser 110 b can sequentially deposit respective materials on theplatform 102 to form a second layer of material. The energy deliverysystem 112 can then cure this second layer of material to form a secondlayer of the green part. As a result, when the support 104 returns toits initial position relative to the platform, two layers of materialshave been deposited and cured.

In some implementations, the printheads can be mounted on the support104 such that the densification material dispenser 108 a and the bindermaterial dispenser 110 a are positioned before the energy deliverysystem 112 and after the powder dispenser 106 a. The densificationmaterial dispenser 108 b and the binder material dispenser 110 b arepositioned before the powder dispenser 106 b and after the energydelivery system 112. The positions of the densification materialdispensers and the binder material dispensers are interchangeable.

In some implementations, the apparatus 100 can include multiple supportseach holding one or more printheads as shown in FIG. 3C. On each supportthat holds more than one printhead, the printheads can be positioned inaccordance with the arrangement disclosed in FIG. 3B.

In some implementations, the apparatus 100 can includes multiple pairsof powder dispensers, with the two pairs configured to dispense adifferent type of powder. For example, as shown in FIG. 3D, theapparatus 100 can include a first pair of powder dispenser 106 a and 106d, and a second pair of powder dispenser 106 b and 106 c. The secondpair of powder dispensers 106 b, 106 c is positioned between the firstpair of powder dispensers 106 a, 106 d. Again, this can permit theapparatus to operate in a bi-directional mode.

For example, in FIG. 3D, the powder dispensers 106 a and 106 d candispense a first powder of a first material composition, e.g. a powdercomprising metal particles, and the powder dispenser 106 b and 106 c candispense powder of a different second material composition, e.g., apowder comprising plastic particles.

In some implementations, the multiple powder dispensers are configuredto dispense powder of the same material composition but of differentsize. For example, in FIG. 3D, the powder dispensers 106 a and 106 d candispense a first powder of a first material composition and fallingwithin a first size range, e.g., larger than 100 nanometers, and thepowder dispenser 106 b and 106 c can dispense a second powder of thesame material composition but falling within a different second sizerange, e.g., smaller than 100 nanometers. The size ranges can benon-overlapping.

In some implementations, the apparatus 100 can include multiple pairs ofbinder material dispensers, with the two pairs configured to dispensedifferent types of binder material. For example, as shown in FIG. 3E,the apparatus 100 can include a first pair of binder material dispensers110 a and 110 d, and a second pair of binder material dispensers 110 band 110 c. The second pair of binder material dispensers 110 b, 110 c ispositioned between the first pair of binder material dispensers 110 a,110 d. Again, this can permit the apparatus to operate in abi-directional mode.

In some implementations, the different pairs of multiple binder materialdispensers are configured to dispense different types of bindermaterials. The binder materials from dispensed from dispensers 110 a and110 d can differ in viscosity, curing wavelength, curing kinetics,and/or wetting behavior from the binder material dispensed fromdispenser 110 b and 110 c, for the various reasons discussed above. Forexample, in FIG. 3E, the binder material dispenser 110 a and 110 d areconfigured to dispense binder material operable on powder from thepowder dispenser 106 a and 106 d, respectively, while the bindermaterial dispenser 110 b and 110 c are configured to dispense bindermaterial operable on powder from the powder dispensers 106 b and 106 c,respectively.

Although FIGS. 3D and 3E illustrate the various dispensers all on thesame support 104, as discussed above, some of the dispensers can be onseparately movable supports. For example, the two powder dispensers 106a, 106 b could be on a first support, the binder material dispensers 110a-110 d and energy delivery system 112 could be on a second support, andthe two powder dispensers 106 c, 106 d could be on a third support.Alternatively, each powder dispenser 106 a-106 d could be on its ownseparately movable support. The densification material dispensers 108 a,108 b, could be on their own support, or on the support of one of theadjacent dispensers.

FIG. 4 shows an example of the additive manufacturing apparatus 100fabricating a three-dimensional part, e.g., a green part.

The powder dispenser 106 first dispenses a layer of powder particles 116onto the platform 102 at desired locations, i.e., it has a lateralspatial resolution. The lateral resolution of the powder dispenser canbe worse, i.e., lower, then lateral resolution of the binder materialdispenser. For example, binder material dispenser can dispense bindermaterial on a voxel-by-voxel basis to an uppermost layer of powder inthe build area to form a volume of the layer having powder and bindermaterial and corresponding to a cross-sectional portion of a part beingbuilt. In contrast, the powder dispenser can be configured toselectively dispense the powder on a region-by-region basis, where theregions are larger than the voxels. While there may still be some powderdelivered in areas where it is unneeded, this still permits usage ofpowder to be reduced. In some implementations, the lateral resolution ofthe powder dispenser is the same, e.g., voxel-by-voxel, as the lateralresolution of the binder material dispenser.

In some implementations, a mechanical roller or blade 401 is employed tosubsequently spread and/or compact the thin layer of powder particles116.

The amount of powder particles 116 required per layer is determined bythe controller 111 based on a number of factors, including but are notlimited to: the pre-determined layer thickness, the size of theparticles, the size of the green part and or the retaining wall, thedesired spatial resolution, the effective printing area, etc. Thecontroller 111 has a memory configured to store a data object thatidentifies a pattern controlling the movement and material dispensing ofthe printheads.

In some implementations, the densification material dispenser 108dispenses the densification material 118 at selected locations on thepreviously spread layer of the powder particles 116. For example, thedensification material can be deposited at regions corresponding to thesurface of the object being fabricated. The densification material 118can serve several different purposes. For example, the densificationmaterial 118 can help fill the space between the neighboring powderparticles 116, thus improving the green part's density, reducedshrinkage and rigidity.

In some implementations, the densification material 118 is or includes apowder of particles. Such densification particles 118 can act asnucleation sites during the post-processing of the green part, resultingin stronger bonding and lower sintering temperature. In someimplementations, the densification material 118 comprises particles ofsimilar or identical chemical compositions as that of powder particles116. In particular, both the powder particles and the particles of thedensification material can be ceramic particles. Alternatively, thedensification material 118 can comprise particles of varied chemicalcompositions that act as both densification agents and chemical dopants.

The particles of the densification material 118 can be nano-particles.For example, the particles can have a mean diameter of 10 to 1000 nm,e.g., 50 to 500 nm. In contrast, the powder particles 116 can have amean diameter between 2 and 100 times, e.g., between 3 and 50 times,between 2 and 10 times, or between 10 and 20 times, larger than the meandiameter of the particles of the densification material 118. In someimplementations, the powder particles 110 have a mean diameter between 1and 500 μm, e.g., between 5 and 50 μm, e.g., between 5 μm and 10 μm, thedensification particles have a mean diameter between 10 nm and 10 μm,e.g., between 10 nm and 1 μm, e.g., between 10 nm and 100 nm.

In some implementations, the densification material 118 includesparticles mixed with a carrier fluid or gel. For example, thedensification material 118 can include nano-particles mixed with a gel,e.g., a sol-gel. The sol-gel can be a precursor for a ceramic material,e.g., the same ceramic material as the powder particles. As anotherexample, the densification material 118 can include nano-particles mixedwith a carrier fluid. Alternatively, the densification material 118 canbe a liquid.

In some implementations, the densification particles 118 can be mixedwith the binder material 120 a prior to dispensing. In this case, asingle dispenser can deliver a mixture of the binder material anddensification particles onto the build area.

A blade and/or roller can be used to obtain a smooth uniform layer priorto the binder material being dispensed and cured. In the case ofnano-scale densification agents, a combination of blade and roller canbe employed to dislodge, push and spread the densification agent intothe layer.

In some implementations, densification particles 118 can be mixed withthe binder material 120 a prior to dispensing. In this case, a singledispenser can deliver a mixture of the binder material and densificationparticles onto the build area.

Once a layer 130 of powder particles 116 and densification particles 118has been spread and compacted on the platform 102, the binder materialdispenser 110 can selectively place the binder material 120 a onto thelayer 130.

As shown in FIG. 4A, the binder material dispenser 110 places the bindermaterial 120 a on the layer 130 of powder and densification material.

In some implementations, the binder material dispenser 110 can dispensethe binder material 120 a via ink-jetting (in which case the bindermaterial can be dispensed in droplets), pipetting, contact transfer,imprint transfer, etc. In some implementations, binder material 120 acan infiltrate the space between powder particles 116. In someimplementations, the binder material is a liquid. In someimplementations, the binder material is solid; in this case theparticles of the binder material should be smaller than the powder sothat the binder material will infiltrate into the powder.

Once binder material 120 a have been placed at the selected locations onthe layer 130 of powder particles 116 and densification material 118,the energy delivery system 110 can deliver a radiation beam 122 thatcauses the binder material 120 a to solidify, e.g., polymerize, aroundboth powder particles 116 and optional densification particles 118. Thisresults in the powder particles 116 held in a matrix of binder material120 a.

Examples of radiation beam 122 include, but are not limited to,electron-beam, thermal radiation, UV radiation, IR radiation,monochromatic radiation, microwave radiation, etc. As a result ofcuring, cured binder material 120 b can act as glue to physically couplethe neighboring powder particles 116 and 118 together. Cured bindermaterial 120 b bonds particles within the same layer, and can bondparticles in adjacent layers. In some implementations, the bindermaterial can be formulated to be water-soluble or solvent-soluble. Insome implementations, the binder material 120 a can be thermal orUV-curable polymers. In some implementations, the binder material 120 acan be either colorless or of a specific color.

The successive application of powder particles 116, densificationparticles 118, binder material 120 a, and radiation beam 122 results inthe formation of the green part in a pool of loose powder particles 116.

In an apparatus with multiple powder dispensers which can eachselectively dispense a respective powder, different powders can beprovided for different regions.

FIG. 4B shows examples of different regions in dispensed layer ofpowder, binder, and densification materials. For example, powder can bedispensed in a retaining wall region 403 surrounding and separated fromthe perimeter of the object to be fabricated. This powder is held inplace with cured binder material 120 b to form a retaining wall 403. Thepowder in the retaining wall 403 can be of the same or differentcomposition from the composition of the powder used to form the object.For example, if the powder for the green part is a metallic powder, thenthe powder for the retaining wall can be ceramic powder or plasticpowder. As another example, if the powder for the green part is aceramic powder, then the powder for the retaining wall can be a plasticpowder.

The retaining wall 403 surrounds both a green part region 407 containingthe layer of the green part being fabricated and a buffer region 405containing loose powder particles. The loose powder particles are powderparticles not bounded by the cured binder material 120 b and providelateral support to prevent the powder in the green part region fromslipping laterally. The loose powder particles in the buffer region 405can also provide vertical support for powder particles in a subsequentlayer. The buffer region 405 separates the retaining wall 403 from thegreen part region 407 to prevent the retaining wall from binding to thepart. As a result, the green part can be easily removed from theplatform 102 once finished. The powder in the buffer region 405 can beof the same or different composition from the composition of the powderused to form the object. For example, if the powder for the green partis a metallic powder, then the powder for the buffer region can beceramic powder or plastic powder. As another example, if the powder forthe green part is a ceramic powder, then the powder for the bufferregion can be a plastic powder. To improve structural rigidity of thepart during build, horizontal ‘bridges’ or ‘tethered structures’ can beformed by selectively placing binder materials in the buffer regions405.

Once the green part is formed, it is removed from the platform 102 andthe unbound powder particles 116 are recycled by the additivemanufacturing apparatus 100 for future use. The green part is thensubject to further processing to solidify the powder into a solid mass,and thus increase the density or rigidity of the final product. Examplesof green part post-processing include, but are not limited to, sinteringand annealing. The presence of densification particles 118 reduces thedegree of green part shrinkage during these post-processing steps. Thebinder material can evaporate or melt away during the subsequentprocessing.

In some implementations, the powder dispenser 106 and the densificationmaterial dispenser 108 are configured to selectively dispense respectiveparticles.

The powder dispenser 106 can include a plurality of nozzles suspendedabove the platform 102 through which the powder flows. For example, thepowder could flow under gravity, or be ejected, e.g., by piezoelectricactuator. Control of dispensing of individual nozzles could be providedby pneumatic valves, microelectromechanical systems (MEMS) valves,solenoid valves, and/or magnetic valves. Other systems that can be usedto dispense powder include a roller having controllable apertures, andan auger inside a tube having multiple controllable apertures.

The powder can be a dry powder or a powder in liquid suspension, or aslurry suspension of a material. For example, for a dispenser that usesa piezoelectric printhead, the feed material would typically beparticles in a liquid suspension. For example, a dispenser could deliverthe powder in a carrier fluid, e.g. a high vapor pressure carrier, e.g.,Isopropyl Alcohol (IPA), ethanol, or N-Methyl-2-pyrrolidone (NMP), toform the layers of powder material. The carrier fluid can evaporateprior to the sintering step for the layer. Alternatively, a drydispensing mechanism, e.g., an array of nozzles assisted by ultrasonicagitation and pressurized inert gas, can be employed to dispense theparticles.

FIG. 5A shows an example of the powder dispenser 106 configured toselectively dispensing powder particles 116 toward the platform 102. Thepowder dispenser 106 comprises multiple individually controllable microdispensers 106 a, each capable of dispensing powder particles 116.

The micro dispensers 106 a are positioned such that each micro dispenser106 a can dispense powder particles 116 to a corresponding area of thegreen part to be formed. Such an arrangement of the micro dispensers 106a enables the micro dispensers 106 a to selectively dispense multiplepowder particles 116 extending along the Y-axis at once withoutrequiring relative motion between the powder dispenser 106 and theplatform 102 along the Y-axis.

FIG. 5B shows schematic examples of the micro dispenser 106 a. Forexample, the micro dispenser 106 a can be controlled by a valve actuator501 at the dispenser's opening. The valve actuator 501 opens to causethe flow of powder under gravity. In another example, the micro dispense106 a can be controlled by a micro gear 502 at the dispenser's opening.The micro gear 502 can rotate to cause the flow of powder due to thefriction force between the micro gear 502 and powder particles 116.

In some implementations, the geometrical shapes of the opening of themicro dispenser 106 a can include circle, triangle, elongated slot,square, etc.

As the powder dispenser 106 scans across the platform 102, themicro-dispenser 106 a are operated to selectively dispense powder ontothe build rea. For example, the micro dispensers 106 a can be operatedto dispense a first set of powder particles 116 along a first column ofvoxels of the part while the powder dispenser 106 is at a first positionalong the X-axis, and then dispense a second set of powder particles 116along a second column of voxels offset from the first set of voxelswhile the powder dispenser is at a second position along the X-axis.Motion of the powder dispenser 106 can be continuous during dispensingof the powder, or powder dispenser can move in steps between dispensingoperations with the powder dispenser being stationary during dispensingto a particular column of voxels.

The array of the micro dispensers 106 a extends along the Y-axis, e.g.,in a direction perpendicular to the direction of relative motion of theplatform 102 and the support 104. In some implementations, the array ofthe micro dispensers 106 a extends across an entire width of theplatform 102. The support 104 scans along the X-axis so that the microdispensers 106 a can selectively dispense powder particles 116 acrossthe entire platform 102.

In some implementations, the array of the micro dispensers 106 a extendsalong a direction of motion of the platform 102, e.g., along the X-axis.The micro dispensers 106 a are thus capable of dispensing powderparticles 116 along the X-axis. As a result, a number of increments ofrelative motion between the support 104 and the platform 102 along theX-axis to cause the micro dispensers 106 a to scan across an entirelength of the platform 102 can be decreased.

In some implementations, the array of micro dispensers 106 a extendsalong both the X-axis and Y-axis. For example, the array of microdispensers 106 a can form a rectangular array in which the microdispensers 106 a are arranged in parallel rows and columns.Alternatively, adjacent columns of micro dispensers 106 a are staggeredrelative to one another, or adjacent rows of micro dispensers 106 a arestaggered relative to one another.

In some implementations, the array of micro dispensers 106 a extendsalong the X-axis and Y-axis such that the array of micro dispensers 106a extends across the platform 102. During relative motion of theplatform 102 and the support 104, the platform 102 is positionedrelative to the array of micro dispensers 106 a such that the build areais beneath the array of micro dispensers 106 a and such that the microdispensers 106 a can directly dispense powder particles 116 toward anyportion of the build area for the green part.

In some implementations, the binder material dispenser 110 and thedensification material dispenser 108 can be configured with architecturesimilar to the powder dispenser 106 described above, albeit withdifferent materials and dispensing mechanisms (e.g., the binder materialdispenser could use a piezoelectric actuator to eject droplets of liquidbinder material).

FIG. 6 illustrates an example process 600 to form a green part. Forexample, the apparatus 100, including the controller 111, can executethe process 600.

Relative motion between the support 104 and the platform 102 isgenerated (602). For example, one or more actuators 127 a can beoperated by the controller 111 to generate the relative motion. Therelative motion is controlled so that the printhead assembly 103 can berepositioned to a target location where powder particles 116,densification particles 118, and binder particles 120 are to beselectively dispensed.

A layer of powder particles 116 is dispensed on the platform 102 (604).For example, the printhead assembly 103 can be operated by thecontroller 111 to dispense powder particles 116. Referring also to FIG.5, the controller 111 can control how the micro dispensers 106 adispense powder particles 116. If the powder dispenser 106 does notextend across an entire width of the platform 102 and is movablerelative to the support 104, in some implementations, at operation 604,the powder dispenser 106 scans along Y-axis to dispense powder particles116 along the entire width of the platform 102.

Optionally, densification particles 118 are dispensed at selectedlocations on the layer of powder particles 116 (606). For example, thedensification material dispenser 108 can be operated by the controller111 to dispense densification particles. If the densification materialdispenser 108 does not extend across an entire width of the platform 102and is movable relative to the support 104, in some implementations, atoperation 606, the densification material dispenser 108 scans alongY-axis to dispense densification particles 118 along the entire width ofthe platform 102.

Binder material 120 is dispensed at selected locations on the layer ofpowder-densification particle mixture (608). If the binder materialdispenser 110 does not extend across an entire width of the platform 102and is movable relative to the support 104, in some implementations, atoperation 608, the binder material dispenser 110 scans along Y-axis todispense binder particles 120 a along the width of the platform 102.

Energy delivery system 112 solidifies the binder material 120 a to forma layer in which the powder particles are held in a solidified matrix ofthe binder material. For example, the energy delivery system can curethe liquid binder material 120 b.

The controller, e.g., the controller 111, can be implemented in digitalelectronic circuitry, or in computer software, firmware, or hardware, orin combinations of them. The controller can include one or more computerprogram products, i.e., one or more computer programs tangibly embodiedin an information carrier, e.g., in a non-transitory machine readablestorage medium or in a propagated signal, for execution by, or tocontrol the operation of, data processing apparatus, e.g., aprogrammable processor, a computer, or multiple processors or computers.A computer program (also known as a program, software, softwareapplication, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a standalone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program can be deployed to be executed on onecomputer or on multiple computers at one site or distributed acrossmultiple sites and interconnected by a communication network.

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

The controller 111 and other computing devices part of systems describedcan include non-transitory computer readable medium to store a dataobject, e.g., a computer aided design (CAD)-compatible file thatidentifies the pattern in which the feed material should be formed foreach layer. For example, the data object could be a STL-formatted file,a 3D Manufacturing Format (3MF) file, or an Additive Manufacturing FileFormat (AMF) file. For example, the controller could receive the dataobject from a remote computer. A processor in the controller 111, e.g.,as controlled by firmware or software, can interpret the data objectreceived from the computer to generate the set of signals necessary tocontrol the components of the apparatus 100 to deposit and/or cure eachlayer in the desired pattern.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made.

Thickness of each layer of the layers of powder particles 116 and sizeof each of the voxels may vary from implementation to implementation. Insome implementations, when dispensed on the platform 102, each voxel canhave a width of, for example, 10 μm to 1 mm, e.g., 10 μm 50 μm (e.g., 10μm to 30 μm, 20 μm to 40 μm, 30 μm to 50 μm, approximately 20 μm,approximately 30 μm, or approximately 50 μm), or 50 μm to 1 mm (e.g., 50μm to 300 μm, 50 μm to 100 μm, 100 μm to 300 μm). Each layer can have apredetermined thickness. The thickness can be, for example, 10 μm to 125μm (e.g., 10 μm to 20 μm, 10 μm to 40 μm, 40 μm to 80 μm, 80 μm to 125μm, approximately 15 μm, approximately 25 μm, approximately 60 μm, orapproximately 100 μm).

The powder can include metallic particles. Examples of metallicparticles include metals, alloys and intermetallic alloys. Examples ofmaterials for the metallic particles include aluminum, titanium,stainless steel, nickel, cobalt, chromium, vanadium, and various alloysor intermetallic alloys of these metals.

The powder can include ceramic particles. Examples of ceramic materialsinclude metal oxide, such as ceria, alumina, silica, aluminum nitride,silicon nitride, silicon carbide, or a combination of these materials,such as an aluminum alloy powder.

In some implementations, the powder particles 116 can a mean diameterbetween 1 and 500 μm, e.g., between 5 μm and 50 μm, e.g., between 5 μmand 10 μm, between 10 μm and 100 μm.

In some examples, the additive manufacturing apparatus 100 includes 1,2, or 3 printheads have been described. Alternatively, the apparatus 100includes four or more printheads. Each of the printheads is, forexample, mounted onto the support 104. The printheads are thus movableas a unit across the platform 102. In some examples, the printheads canbe mounted on different supports and are movable independent of eachother. In some cases, the apparatus 100 includes 8 or more printheads,e.g., 8 printheads, 12 printheads, etc. that are aligned along thescanning direction.

Numerous examples are given in the above description with specificdetails; however, it is understood that these examples may be practicedwithout limitations to these specific details. Furthermore, it isunderstood that the examples may be used in combination with each other.

Although the apparatus has been described in the context of fabricatingarticles using binder jetting, the apparatus can be adapted forfabrication of articles by other powder-based methods. For example

-   -   In some implementations, the densification material dispenser        108 is optional. For example, the energy delivery system 112        cures a layer of only powder and binder material.    -   In some implementations, the energy delivery system 112 is        optional. For example, binder material 120 can self-cure by        cooling and does not require additional radiation beam 122.    -   In some implementations, the binder material dispenser is        optional. For example, if the system is to be used to fabricate        a final part (rather than a green part), then powder can be        delivered by one or more of the dispensers 106, and the energy        delivery system can be used to fuse the powder on the platform.    -   The energy source can be on a separate support rather than on        the same support as the binder material dispenser.        Alternatively, the energy source could be immobile relative to        the platform, and be configured to fuse the entire layer        simultaneously.

Accordingly, other implementations are within the scope of the claims.

What is claimed is:
 1. An additive manufacturing apparatus comprising: aplatform; one or more supports positioned above the platform; anactuator coupled to at least one of the platform and the one or moresupports and configured to create relative motion therebetween such thatthe one or more supports scan across the platform, a first dispensersystem configured dispense a plurality of successive layers of powderonto a build area supported by the platform, wherein the first dispensersystem includes a first powder dispenser that is attached to and moveswith a first support from the one or more supports and is configured toselectively dispense a first powder onto the build area, and a secondpowder dispenser that is configured to selectively dispense the secondpowder onto the build area; a second dispenser system configured todispense a binder material onto the build area, wherein the seconddispenser system includes a first binder material dispenser configuredto selectively dispense a first binder material on a voxel-by-voxelbasis to an uppermost layer of powder in the build area to form a volumeof the layer having powder and binder material and corresponding to across-sectional portion of a part being built; and an energy sourceconfigured to emit radiation toward the platform so as to solidify thebinder material.
 2. The apparatus of claim 1, wherein the first powderdispenser comprises a first plurality of individually controllableorifices, each orifice of the first plurality of orifices of the firstpowder dispenser configured to controllably deliver the first powder,and the second powder dispenser comprises a second plurality ofindividually controllable orifices, each orifice of the second pluralityof orifices of the second powder dispenser configured to controllablydeliver the second powder.
 3. The apparatus of claim 1, wherein thesecond powder dispenser is attached to and moves with the first support.4. The apparatus of claim 3, wherein the first binder dispenser and theenergy source are supported by the first support.
 5. The apparatus ofclaim 1, wherein the second powder dispenser is supported by and movablewith a second support from the one or more supports.
 6. The apparatus ofclaim 5, and wherein the second support is movable along a third axis,and the second powder dispenser is configured to selectively dispensethe second powder in a strip along a fourth axis that is at a non-zeroangle relative to the third axis.
 7. The apparatus of claim 6, whereinthe first binder material dispenser and energy source are attached toand move with a third support from the one or more supports.
 8. Theapparatus of claim 6, wherein the third axis is substantially parallelto the first axis.
 9. The apparatus of claim 6, wherein the third axisis substantially perpendicular to the first axis.
 10. The apparatus ofclaim 1, comprising a controller having a memory configured to store adata object that corresponds to at least a layer of an object to befabricated, the controller configured to configured to cause the firstdispenser system to dispense the first powder in a region correspondingto the object to be fabricated, cause the fourth dispenser system todispense the second powder in a region that does not correspond toobjects to be fabricated.
 11. The apparatus of claim 10, wherein thefirst powder comprises metal particles and the second powder comprisesceramic particles, or the first powder comprises metal or ceramicparticles and the second powder comprises plastic particles.
 12. Theapparatus of claim 11, wherein the controller is configured cause thefirst dispenser system to dispense binder material on only the firstpowder.
 13. The apparatus of claim 11, wherein the controller isconfigured cause the first dispenser system to dispense binder materialon both the first powder and the second powder.
 14. The apparatus ofclaim 1, comprising a controller having a memory configured to store adata object that corresponds to at least a layer of an object to befabricated, the controller configured to configured to cause the firstdispenser system to dispense the first powder in a first regioncorresponding to the object to be fabricated, cause the fourth dispensersystem to dispense the second powder in a portion of the first region.15. The apparatus of claim 14, wherein the second powder comprises adensification material for the first powder.
 16. The apparatus of claim1, wherein the second dispenser system comprises a second bindermaterial dispenser to dispense the binder material.
 17. The apparatus ofclaim 16, wherein the first powder material dispenser, second powdermaterial dispenser, first binder material dispenser and second bindermaterial dispenser are attached to and move with the first support. 18.The apparatus of claim 16, wherein the first powder dispenser, firstbinder material dispenser, energy source, second binder materialdispenser and second powder dispenser are arranged in the aforementionedorder along a direction of motion of the first powder dispenser acrossthe support.
 19. The apparatus of claim 18, wherein the second powderhas a same material composition and size distribution as the firstpowder.
 20. The apparatus of claim 18, comprising a controller having amemory configured to store a data object that identifies a pattern inwhich the binder material is to be solidified in a successive layers ofan object to be fabricated, the controller configured to configured tocause the first powder dispenser to dispense a first layer of powder asthe first powder dispenser moves in a first direction along the firstaxis; cause the first binder dispenser to dispense a first layer ofbinder material on the first layer of powder to provide a first combinedlayer of powder and binder material as the first binder materialdispenser moves in the first direction along the first axis, control theenergy source to solidify the binder material in the first combinedlayer in accord with the pattern, cause the second dispenser system todispense a second layer of powder as the second powder dispenser movesin a second direction opposite to the first direction along the firstaxis, cause the second binder dispenser to dispense a second layer ofbinder material on the second layer of powder to provide a secondcombined layer of powder and binder material as the second binderdispenser moves in the second direction, and control energy source tosolidify the binder material in the second combined layer in accord withthe pattern.